Sorry A, not a reply, but something on similar lines.
I’ve just been away for 8 weeks and got home to find 3 tomato plants, about 2 ft tall in my unheated greenhouse, one having a tiny truss on. No chance I presume ?

I would say no as there are too many things against them flourishing. Lack of warm temperature, shortening of daylight hours and the risk of fungal problems. I would discard and wait until springtime.

I would suspect that the cost of heating and lighting a greenhouse over winter just for a few seedlings would far outstrip the cost of buying or growing new plants next year.
You could try a few in a pot on a window sill in the house to see what happens.

I also think it is not cost effective. I often find seedlings grow happily in spring, at least the seeds have survived the winter.